Air Distribution Flashcards
6 cards from real NATE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Air Distribution flashcards as text
What is the purpose of a zone damper in a zoned HVAC system?
Answer: Open or close to direct conditioned air to specific zones based on thermostat demand
Zone dampers are motorized dampers controlled by zone thermostats that open to allow airflow to calling zones and close for non-calling zones.
What type of duct fitting causes the most turbulence and pressure drop?
Answer: Square elbow without turning vanes
Sharp square elbows cause severe turbulence and high pressure drop; long-radius elbows or elbows with turning vanes greatly reduce this loss.
What does the ASHRAE 62.2 standard address in residential applications?
Answer: Ventilation and acceptable indoor air quality for residential buildings
ASHRAE 62.2 specifies minimum mechanical ventilation rates to maintain acceptable indoor air quality in residences.
What is a bypass damper used for in a zoned duct system?
Answer: Relieve excess static pressure when zone dampers close by routing air back to the return side
When zone dampers close, the bypass damper opens to maintain minimum airflow across the coil and prevent equipment damage from excessive static pressure.
What is the correct method for measuring total external static pressure (TESP) on an air handler?
Answer: Measure static pressure in the return plenum before the coil and in the supply plenum after the coil, then subtract return from supply
TESP = supply static pressure minus return static pressure (both measured close to the air handler), giving total system resistance.
What is the recommended insulation R-value for ducts installed in unconditioned attics in most US climate zones?
Answer: R-8
Most US energy codes and ACCA guidelines recommend R-8 duct insulation for ducts in unconditioned attic spaces to minimize heat gain or loss.